Lead J from KQJ...
...should I have?

Seeing as I couldn't lead my partner's ♦, my obvious lead was K♣ - although I had little hope of running them - surely my partner would be void or singleton!

Partner failed to overtake my K (a slip-up for which she later apologised, to give her credit). Winning the A on round 2, she ventured K♦; declarer ducked the first round, took the marked finesse, and all was over....

Question, would I have given us a better chance by leading the Jack from KQJxxxx? A blatant false-card, yes, but then partner, "knowing" that I can't possibly have the Q, might play me for KJ10xxx and would obviously go up with the A and then return a ♣ through "declarer's Q"...

Or alternatively, should I have bid my ♣? At that vulnerability and void in partner's suit, I decided not to.

Leading the King is standard and was the correct choice and is the start of the vital exchange of information between the defenders.
Although they are known as "Standard" leads.1000s of bridge players get them wrong Result? Their defence starts
in confusion. You may be thinking why are these leads so important ? Holding KQJ you would think they are all the same value
And they are ...to YOU But you have a partner,you are not trying to defeat declarer single handedly. In defence,your partner is just as important
as you are. And.because neither of you can see the others hand,the only way to concoct a plan is to pass information by means of the cards you play
Lead the wrong card,as in leading the Jack in this case,and you tell a lie.
Unfortunate that your partner failed to unblock but its a lesson for the future!

"It is not enough to be a good player, you must also play well"
- Dr Tarrasch(1862-1934)German Chess Grandmaster

Bridge is a game where you have two opponents...and often three(!)

"Any palooka can take tricks with Aces and Kings; the true expert shows his prowess
by how he handles the two's and three's" - Mollo's Hideous Hog

Bidding 2C would not be silly. You will usually double with genuine values, so your holding is within the parameters for the bid. But the best reason not too bid 2C is that you have a good lead (with this club holding, I wouldn't consider a diamond lead, even if I had one).

Not only would bidding 2c not be silly, to me not bidding 2c is extremely silly. You have SEVEN clubs and no outside entry. It will be extremely common for partner to hold 0-2 clubs, declarer with Ax/Axx of clubs or something, he ducks once and puts you out of the game at NT defense. You have 6 tricks on offense, maybe only one on defense. So declare. It will be unlucky if partner can't come up with a couple tricks for you to make. And if not then often 1nt was making, no big loss.

There's no reason 2c should get you any higher than 2c; 2c is non-forcing with standard agreements. (With good hands that want to force, you double 1nt for penalties first, or cue bid 2nt with extreme shape that wants to force to a suit game).

Not to mention making 3c for 110 is lot better than +50 at MP. (trump lead doesn't hold to two, look again Cyberyeti).

Seeing as I couldn't lead my partner's ♦, my obvious lead was K♣ - although I had little hope of running them - surely my partner would be void or singleton!

Partner failed to overtake my K (a slip-up for which she later apologised, to give her credit). Winning the A on round 2, she ventured K♦; declarer ducked the first round, took the marked finesse, and all was over....

Question, would I have given us a better chance by leading the Jack from KQJxxxx? A blatant false-card, yes, but then partner, "knowing" that I can't possibly have the Q, might play me for KJ10xxx and would obviously go up with the A and then return a ♣ through "declarer's Q"...

Or alternatively, should I have bid my ♣? At that vulnerability and void in partner's suit, I decided not to.

If only....

Sir,the way we play it we will always bid 2C on the given hand.Not only that but ,with our understanding, partner will always compete upto 3C. We will always lead the CK as the suit is a 7 card suit .Partner who is a bookworm shall overtake and return the suit (which anyone will on seeing the xx in dummy)

Bidding 2C would not be silly. You will usually double with genuine values, so your holding is within the parameters for the bid. But the best reason not too bid 2C is that you have a good lead (with this club holding, I wouldn't consider a diamond lead, even if I had one).

I'll bid 2♣ 100% of the time with this hand. If PD doesn't know this is NF and hoping to play, I'll soon be looking for a new one. Good lead or not, much of the time declarer has the ace ♣ and can hold up long enough to shut me out.

Leading against 1 NT was the question. With my regular partner or with a "known" sound partner there is no doubt: ♣ K. With a nondistinguished partner ♣ Q might work. The problem with ♣ Q can be concealing ♣ K.

Seeing as I couldn't lead my partner's ♦, my obvious lead was K♣ - although I had little hope of running them - surely my partner would be void or singleton!

Partner failed to overtake my K (a slip-up for which she later apologised, to give her credit). Winning the A on round 2, she ventured K♦; declarer ducked the first round, took the marked finesse, and all was over....

Question, would I have given us a better chance by leading the Jack from KQJxxxx? A blatant false-card, yes, but then partner, "knowing" that I can't possibly have the Q, might play me for KJ10xxx and would obviously go up with the A and then return a ♣ through "declarer's Q"...

Or alternatively, should I have bid my ♣? At that vulnerability and void in partner's suit, I decided not to.

If only....

I would certainly bid 2♣ on the North hand Why not? Its a strong 7 suit headed by sequential honours. The question is,having bid the suit
would your partner be alive of the potential misfit and the subsequent dangers of that situation? I would advise the pair of you to have a
discussion about misfits and how to deal with them when they arise.

"It is not enough to be a good player, you must also play well"
- Dr Tarrasch(1862-1934)German Chess Grandmaster

Bridge is a game where you have two opponents...and often three(!)

"Any palooka can take tricks with Aces and Kings; the true expert shows his prowess
by how he handles the two's and three's" - Mollo's Hideous Hog

How crazy is it to rebid 2♦ as South after a pass from North and East?

You know that West has diamonds. West's diamonds might be AJTXX. 2D doubled could be very expensive if IMPs - do you really want to compete for a risky part-score? But strengthen the suit quality (give yourself the J as well) and it becomes more reasonable.